Neither Federal Reserve tapering nor poor economic data appears capable of stopping the broad-based S&P 500, which is now up more than 25% year to date. For skeptics like me, that's an opportunity to see whether companies have earned their current valuations.

Keep in mind that some companies deserve their current valuations. High-end casino and resort operator Wynn Resorts (WYNN -2.01%) recently notched another 52-week high after an analyst at Goldman Sachs called the growth in Macau sustainable. While Wynn has seen its share of Macau growth slow in 2013, it's well-positioned to take advantage of China's rapidly growing middle- and upper-income classes with its high-margin table games and premier resorts. As affirmation of that strong cash-flow expectation, Wynn boosted its regular dividend 25% to $1.25 per quarter in 2014 and also announced a $3 special dividend in November. 

Still, other companies might deserve a kick in the pants. Here's a look at three that could be worth selling.

Trying to stay afloat
There are few industries that I'd even consider too risky nowadays, but time-and-again shippers find themselves on that short list. This week's stock to avoid is Teekay Tankers (TK -0.21%), a shipper of crude oil that currently employs 28 vessels.

The allure of the shipping industry is pretty simple: demand for crude oil and liquid natural gas is rising around the world, so the need for ships to carry these products -- and eventually the daily charter rates that determine those services -- should be expected to rise. With the U.S. demonstrating strong third-quarter GDP growth of 4.1% and China seeing its GDP trend beginning to inch higher once again, the expectation from investors is that shipping demand is on its way up.

While I agree with this theory over the long run, Teekay isn't in a great position to benefit from this increase in demand thanks to ongoing ship overcapacity from its peers, which is keeping charter rates near their lows. The good news is that Teekay and most of its competitors aren't adding any new ships to their fleets -- but it will take years to retire older ships to free up capacity in a meaningful way.

My other qualm with Teekay is its excessive net-debt position. I understand that it takes a lot of money to purchase a fleet of tankers, so I'm not faulting Teekay or any of its peers for utilizing debt to grow fleet size. However, with nearly $6.5 billion in net debt, the interest payments alone are enough to make me think twice about owning this stock.

With a huge rally already in the books and Teekay struggling to get back to profitability, I'd rather let this stock set sail without me.

A mind-boggling ascent
Occasionally, the laws of gravity don't seem to apply to small-cap companies in slow-growth sectors, which is exactly the case with Xerium Technologies (NYSE: XRM), a supplier of consumable products for the paper industry.

If you've been keeping up with the paper or textile industries in recent quarters, you're probably well aware that growth of any sort is coming at a premium right now. While some consolidation and cost-cutting have boosted interest in the sector, sales growth just hasn't been there. In Xerium's third-quarter, it delivered a paltry 0.2% increase in sales as its backlog actually shrank to $156 million from the sequential quarter. Although the company's EBITDA improved, that was mainly attributable to its ongoing cost-cutting effort, not genuine organic growth. 

Looking back even further, out of the past 10 quarters that Wall Street has covered Xerium, it has missed EPS estimates by a mile in seven of them, with revenue growth practically nonexistent. In other words, I don't have the slightest clue what Wall Street or investors see in Xerium relative to the rest of the paper-products sector.

My suggestion would be to avoid the allure of this pretty chart and forward P/E of 13 and dig deeper to expose Xerium's lack of top-line growth. Unless Xerium goes on the acquisition offensive, it could be tough to maintain the robust gains it achieved in 2013.

Desperate times call for desperate measures
The past few weeks have certainly been Christmas-like for shareholders of Idenix Pharmaceuticals (NASDAQ: IDIX), a clinical-stage developer of hepatitis-C therapies. Over that time period, Idenix's shares have vaulted higher by greater than 50% following the approval of Gilead Sciences (GILD -0.30%) hepatitis-C drug, Sovaldi, by the Food and Drug Administration.

It's been Idenix's contention that Gilead intruded upon two of its patent rights with Sovaldi, and in a recent ruling by the U.S. Patent and Trademark Office, Idenix was named the senior party, meaning it is up to Gilead to prove that it discovered these patents prior to Idenix -- otherwise it could be forking over a settlement or royalties to Idenix. 

While the potential income stream from Sovaldi is impressive and a favorable court ruling would be a welcome surprise for shareholders, I'd rather not speculate on a court battle which can drag on for years and instead focus on Idenix's numerous pipeline setbacks over the past three years. As I've chronicled previously, Idenix scrapped IDX320, IDX184, and IDX19386 for safety and/or efficacy reasons since 2010, and earlier this year it was dealt another blow, with IDX20963 placed on clinical hold by the FDA. No wonder my Foolish colleague Brian Orelli refers to Idenix as the most unlucky biotech ever!

The concern with Idenix here is that even if it does reach a settlement with Gilead, its pipeline can't seem to get anything past a mid-stage trial. It's Idenix's pipeline, not its luck in the courtroom, that will determine its long-term value, and at the moment I'm just not seeing enough positives to justify this current valuation.